#include<stdio.h>
#include<unistd.h>

int g_val = 100;

int main()
{
    int cnt = 0;
    pid_t id = fork();
    if(id == 0)
    {
        while(1)
        {
            printf("I am child process,pid:%d,ppid:%d, g_val:%d,&g_val:%p\n",getpid(),getppid(), g_val, &g_val);
            sleep(1);
            cnt++;
            if(cnt == 5)
            {
                g_val = 300;
                printf("I am child process, change:%d->%d\n", 100, 300);
            }
        }
    }
    else 
    {
        //father
        while(1)
        {
            printf("I am child process,pid:%d,ppid:%d, g_val:%d,&g_val:%p\n",getpid(),getppid(), g_val, &g_val);
            sleep(1);
        }
    }
    return 0;
}
